Variable cut-off for steam-engines



ADDISON CROSBY,

OF FREDONIA,

YE7 YORK.

VARIABLE CUT-OFF FOR STEAM-ENGINES.

Specication of Letters Patent No. 19,134, dated January 19', 1858.

To aZZ whom t may concern.'

Be it known that I, ADDrsoN CROSBY, of Fredonia, in the county ofChautauqua and State of New York, have invented a new and ImprovedVariable Cut-Off for Steam- Engines; and I do hereby declare that thefollowing is a full, clear, and exact description of the same, referencebeing had to the accompanying drawings, forming part of thisspeciiication, in which- Figure l exhibits an interior view of thesteam-chest of a steam-engine, with a side view of the slide valve,cut-ofi", and mechanism for operating the' latter. Fig. 2 exhibits alongitudinal section of the slide valve and its seat, with acorresponding section of the cut-off. Fig. 3 is a transverse section inthe line of Fig. l. Fig. l is a perspective view of one of the seats ofthe cut-oif valves. Fig. 5 is a perspective View of one of the ringswhich are attached to the cut-olf valves for the purpose of operatingthem.

Similar letters of reference indicate corresponding parts in the severalfigures.

A is the steam chest.

B is a slide valve of well-known kind, for the induction and eduction ofsteam to and from the cylinder, working on a seat a, (L, and moved by aneccentric O, on the crank shaft of the engine.

b, b1, are steam ports, and o, 01, are exhaust ports in the valve seat,the former communicating with the cylinder and the latter with theexhaust pipe.

(Z, (Z1, are induction passages through the valve, and e, e1, areeductio-n cavities for forming communication betwwen the ports Z2, ando, and between those b1, and c1.

D D1, is a sliding box containing two steam chambers D and D1 and fittedto slide on the back of the main valve B, said chambers being separatefrom each other and open on the side next the slide valve to communicaterespectively with the induction passages (Z, (Z1, of the main valve, butbeing closed to the steam chest A, except through the two hollow plugcut-off valve E, E1, whose seats f, f1, extend all the way through theirrespective steam chambers as is shown in Fig. 3, so as to admit steam atall times to the interiors of the cut-off valve E, E1. These valves haveeach several very narrow openings g, g, in their sides to correspondwith the same number of openings j, j, in their respect-ive sea-ts toadmit steam from the chest A to the chambers D, D1,to be suppliedthrough the passages (Z, (Z1, to the cylinder and to cut it off by avery slight movenient circularly in theirl seats.

The two-chambered sliding valve box D D1, is connected with an eccentricF, 011 the crank shaft of the engine, or otherwise so operated that italways moves in the same direction with the engine piston, and throughthis movement the cut-oii' valves E, E1, derive the necessary movementto admit steam to the chambers D and D1, to supply the cylinder and tocut it oil'. The means by which the movement is given to the valves forthe above purpose are as follows: At one end of each valve E, E1, issecured a collar L, or h1, on which there is a projection z', or 1,whichfrom its form (see Fig. l) may be termed a toe and heel piece, andinside the steam chest there is secured near one end of the valve seatafixed piece of metal Z, and near the other end thereof a similar pieceZ1 said pieces being arranged on the same side of the sliding valve boxin such a manner that the toes of the projections z', lZ1, will strikethem as the sliding valve box and the engine piston arrive near the endof their stroke in either direction, and thus cause the cut-off valvesto be opened in their proper turn, by the time the piston completes itsstroke, ready to admit steam to the cylinder as the slide valve B beginsto open the port Z), or 1. On the same side of the sliding valve box asthe toes z', i, there are also arranged two bars Gr, G1,

l provided respectively with shoulders Ze, 701,

on their upper part; said shoulders being so arranged that the heels ofthe projections z', 1, will strike them after the piston and the slidingvalve box have made a certain portion of their stroke and thus cause thecut-off valves to be closed in their proper turn to cut oif the steam.The cutting oit' is made to take place sooner or later in the stroke bychanging the position of the bars G, G1, longitudinally, to throw theirshoulders Za, 701, farther apart or bring them nearer together, and toadmit of this, they are attached to a stationary stand I, within thesteam chest A, by means of screw bolts m, m1, passing through slots 0,01, and provided with pins n, n1, working in slots p, p1, in the stand.The shifting of the bars to vary the point of cutting off is effected bya small shaft g, passing through a stuffing bo'x in the steam chest andcarrying a pinion o, gearing with toothed racks on the two bars, theracks gearing wit-h the pinion on opposite sides of the center thereofso that by the rotation of the latter they will be caused to move inopposite directions, so that the shoulders 7c, 701, will approach orrecede from each other. vThe shaft g, may be operated by hand to adjustthe bars in the desired position to cut off at the proper`- point, orconnected with a governor to govern the engine by varying the point ofcutting off.

I am aware that hollow valves have been before employed upon the back ofa sliding valve; and therefore I do notclaim, broadly, the employment ofhollow valves, except as herein described.

It will be readily understood that the cutoff valves being hollow, andreceiving steam at the interior, and having openings at opposite pointsin themselves and their seats, must receive an equal pressure of steamon all sides, or in other words, are balanced laterally; but owing totheir taper form there is a slight pressure in a longitudinal directiontending to force them into their seats. To prevent the friction thatwould be produced by this longitudinal pressure in turning the saidvalves, I cause them to move a slight distance longitudinally out oftheir seats, as they are turned to open the passages g, and j, by makingthe larger ends of the valve seats f, f1, which project out beyond theside of the valve boX D, D1, with a spiral inclination, or of the formof a single turn of a screw-thread as shown at s, in Fig. 4, and makingthe inner faces of the collars 7L, tl, which work close to the said endsof the seat, of a corresponding form, as shown at t, in Fig. 5. The jogsu, u, on the seats f, f1, and collars 7L, h1, serve as stops to preventthe turning of the cut-off valves farther than is necessary in closing.

That I claim as my invention and desire to secure by Letters Patent is:

rIhe arrangement of the two hollow plug cut-oft1 valves in a doublechambered valve box D, D1, which has a sliding movement on the back ofthe main valve for the purpose of opening and closing the said valves toadmit and cut off the steam, by means of toe pieces z', t', or theirequivalents attached to the latter, coming in contact with suitablepieces within the steam chest, substantially as herein described.

. ADDISON CROSBY.

IVitnesses ALLEN HINCKLEY, A. Z. MADISON.

